The invention relates to gang form bolts for use in holding a tie rod passing through abutting frames of prefabricated panel units.
This invention is an improvement on and an adaptation of the gang form bolt of U.S. Pat. No. 3,756,555, issued to Doubleday et al on Sept. 4, 1973, as assigned to the assignee of the present invention, and hereby incorporated by reference.
The use of prefabricated panels in a gang of formed sections either preassembled or assembled on the job is well known in the concrete pouring art. Such prefabricated units usually have a flat base of plywood or other suitable material of appropriate dimensions reinforced by a metal frame extending around the periphery of each unit. The metal frame is usually of I-shaped cross sections and edges thereof which abutt when the panel units are in position. These edges are suitably cut away to provide space for insertion of tie rods to extend between spaced gang from section between which the concrete is to be poured. The tie rods prevent the weight of the concrete from forcing the gang form sections away from each other.
The prior art includes numerous tie rod holding bolts as shown in the following U.S. Patents:
______________________________________ U.S. Pat. No. Issue Date ______________________________________ 3,067,479 - Schimmel December 11, 1962 3,142,883 - Kort et al August 4, 1964 3,584,827 - Shoemaker June 15, 1971 3,655,162 - Shoemaker April 11, 1972 3,945,602 - Doubleday et al March 23, 1976 4,221,357 - Bowden et al September 9, 1980 ______________________________________
The Schimmel patent discloses a tie rod bolt including a form slot leg and a tie engaging leg. A notch disposed in between the form slot leg and the tie engaging leg is disposed adjacent the back of the frames.
The Kort et al patent discloses a tie rod and anchor bolt combination having a form slot leg and a tie rod engaging leg with two legs in between. The tie rod is curved to straddle the two legs between the slot leg and the rod engaging leg.
The two Shoemaker patents disclose Waler clamp assemblies for concrete wall forms, each assembly including a surface for abutting the back edges of the frames.
The Doubleday et al U.S. Pat. No. 3,756,555, incorporated by reference above, discloses a gang form bolt including a form slot leg, a tie engaging leg and a middle leg. The middle leg has a hold for accomodating a pin to hold the tie rod bolt in place. The form slot leg and the middle leg are in common horizontal plane. The tie rod holding bolt is arranged such that the load on the tie rod is transmitted to the frames by the form slot leg.
The Doubleday et al U.S. Pat. No. 3,945,602 discloses a U-shaped (in cross section) tie rod holding bolt including 2 back edges abutting the frames for load transmission.
The Bowden et al Patent discloses a tie rod assembly wherein the tie rod places a straight axial load on the tie rod holding bolt.
Although the above and other tie rod holding bolts have been generally useful, they are often subject to one or more of number of disadvantages. In particular, an increase in tension in the tie rod often has the tendency to tip the tie rod holding bolt or to bend the tie. Some prior art tie rod holding bolts have been under such tension that, when they are unloaded, the bolt has a tendency to snap off and act as a projectile which may be hazardous to personnel. Prior art designs which may at least partially overcome these problems are generally complex in construction, requiring more pieces than the basic tie rod, tie rod holding bolt and holding pin combination.